The proposed research deals with the representation and processing of magnitude and order information. A major focus concerns the processes by which people can compare two stimuli on the basis of subjective magnitude or relative order in a linear series. Major questions include: (a) how is the judgment process affected by the form of the comparative question, or by an explicit reference stimulus?; (b) how similar are the processes involved in judgments based on memory versus perception?; (c) what is the relationship between order and magnitude information?; (d) what role does magnitude information play in semantic processing? Experiments completed to date have investigated the effects of reference stimuli on ratings of magnitude difference, and the types of semantic recognition errors that are made for sets of ordered concepts.